Alcator C-Mod experiments in support of the ITER baseline 15 MA scenario

Experiments on Alcator C-Mod from 2009-2012 have examined the rampup, flattop and rampdown phases of the proposed ITER 15 MA baseline scenario. Rampup studies show ICRF heating can significantly reduce the V-s requirement, and that an H-mode late in the ramp can reduce this further. ICRF modifications to l(i) in L-mode are minimal, although the T-e profile is peaked relative to ohmic in the plasma centre, and reduces the sawtooth onset times. Flattop plasmas targeting ITER baseline parameters have been sustained for 20 tau(E) or 8 - 13 tau(CR), but only reach H-98 similar to 0.6 at n/n(Gr) = 0.85, rising to 0.9 at n/n(Gr) = 0.65. Rampdown studies show H-modes can be routinely sustained with ICRF power injection, avoiding an OH coil over-current associated with the H-L transition. In addition, faster current rampdowns are preferred to avoid an over-current when an H-L transition ultimately does occur. In the H-mode rampdown the density is found to drop with I-p, preserving the n/n(Gr) ratio, so long as ICRF power is injected.